Why are My MP3 Files the Same Size Even When I Change the Bitrate with FFmpeg?

In the event that you are new to the methodology of changing over sound documents, then a number of the points of interest and how they function can be a bit befuddling when you get surprising results. So what do you do to alter the issue? Today's SuperUser Q&A post has the response to a confounded peruser's inquiry. 


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Today's Question & Answer session comes to us obligingness of SuperUser—a subdivision of Stack Exchange, a group driven gathering of Q&A site

The Question

In the event that you are new to the methodology of changing over sound documents, then a number of the points of interest and how they function can be a bit befuddling when you get surprising results. So what do you do to alter the issue? Today's SuperUser Q&A post has the response to a confounded peruser's inquiry. 

Today's Question & Answer session comes to us obligingness of SuperUser—a subdivision of Stack Exchange, a group driven gathering of Q&A site

• ffmpeg -i “Likoonl-Q1-All.mp4″ -c:v copy -c:a libmp3lame -q:a 1 -b:a 192k “Q1-All-192k.mp4″
• ffmpeg -i “Likoonl-Q1-All.mp4″ -c:v copy -c:a libmp3lame -q:a 1 -b:a 160k “Q1-All-160k.mp4″
• ffmpeg -i “Likoonl-Q1-All.mp4″ -c:v copy -c:a libmp3lame -q:a 1 -b:a 128k “Q1-All-128k.mp4″

How did using different bitrate settings produce files of the same exact size?

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The Answer

SuperUser donor slhck has the response for us: 

Since you are setting -q:a (which is LAME's VBR setting). When you utilize -q:a, the CBR setting -b:a will have no impact. On the off chance that you investigate the MP3 encoding aide from the FFmpeg Wiki, you will discover the conceivable qualities for-q:a with their relating normal bitrate. 

For the purpose of culmination, here is the applicable piece of libmp3lame.c(qscale is the long name of q):

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